[11u] RFR (XS) 8261251: Shenandoah: Use object size for full GC humongous compaction

[Roman Kennke]

Good! Thanks,
Roman

> Original bug:
>    https://bugs.openjdk.java.net/browse/JDK-8261251
>    https://git.openjdk.java.net/jdk/commit/deb0544f
> 
> The patch does not apply cleanly to 11u, because of the 
> shenandoahMarkCompact -> shenandoahFullGC rename. I applied the same 
> patch to the new file without problems.
> 
> 11u variant:
> 
> diff -r a4e1ec47729f 
> src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp
> --- a/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp Thu Jan 
> 28 09:50:21 2021 +0000
> +++ b/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp Mon Feb 
> 15 10:50:03 2021 +0100
> @@ -905,7 +905,7 @@
> 
>         Copy::aligned_conjoint_words(heap->get_region(old_start)->bottom(),
>                                      heap->get_region(new_start)->bottom(),
> -                                   
> ShenandoahHeapRegion::region_size_words()*num_regions);
> +                                   words_size);
> 
>         oop new_obj = oop(heap->get_region(new_start)->bottom());
>         new_obj->init_mark_raw();
> 
> Testing: hotspot_gc_shenandoah; tier{1,2} with Shenandoah
>